Because Hillary Clinton's former chief of staff walked out of an interview with the FBI (a good sign, right?) because someone asked her "off-limits" questions.
"The questions that were considered off limits had to do with the procedure used to produce emails to the State Department so they could possibly be released publicly, the people said. Mills, an attorney herself, was not supposed to be asked questions about that — and ultimately never was in the recent interview — because it was considered confidential as an example of attorney-client privilege, the people said."
I also like this bit:
"Mills and her lawyer left the room — though both returned a short time later — and prosecutors were somewhat taken aback that their FBI colleague had ventured beyond what was anticipated, the people said."
If you haven't been following the case and don't get why that's funny it's because that while this is an FBI investigation, it will ultimately be the Department of Justice who ends up prosecuting (or not) someone, so they get to have a seat in all these interviews by the FBI. But when prosecutors say they were "taken aback" when the FBI asked questions about emails, when the entire case involves... emails, that sounds more like the DOJ is running interference.
p.s. And another thing, why is it that the timeline for all this seems to be some sort of secret? This interview took place "recently" and news that Huma Abedin was interviewed came out last week even though the interview supposedly took place a month ago.